1. Field of the Invention
The present invention relates to an apparatus for the cutoff of a fiber material web, such as a web for paper or cardboard, in a paper machine such as a paper-making machine, rewinder, coater and/or rotary slitter.
2. Description of the Related Art
A cutoff apparatus as described above may be configured with a machinewide knife that extends transverse to the direction of paper travel (see, e.g., DE 38 15 277). The cutting edge of the knife according to DE 38 15 277 has a large distance from the impact point of the cutting edge to the splice on the splicing roll. As a result, an excessively long paper remnant, or paper tail, remains behind the splice after cutoff of the material web and gluing it to a new web. This leads to breaks, for example in a follow-on coater, notably with thin paper grades. Furthermore, the apparatus according to DE 38 15 227 has the further disadvantage that a serrated blade is used, as a result of which the web undesirably has a serrated cutoff edge.
DE-U-94 13 363 shows an apparatus for cutoff of a traveling material web. The apparatus is equipped with a cutoff knife heavily slanted opposite to the direction of web travel and avoids the latter of the aforementioned disadvantages. The angle occurring during the cutoff process between cutoff knife and material web is with the object according to DE-U-94 13 363 smaller than 45 degrees. At low web velocities, a cutoff edge which is extensively straight across the material web can be achieved with it, but, especially with high web velocities, &gt;1500 m/min, the measures according to DE-U-94 13 363 are no longer sufficient to achieve the desired reliability of operation. A factor in addition to the known problems with the above high web velocities is that the cutoff velocity of the cutoff knife is mostly insufficient to achieve a non-serrated cutoff.
What is needed in the art is a cutoff apparatus which overcomes the disadvantages that occur at high web velocities with the prior-art apparatuses.